1. Field of the Invention
The present invention relates to a tool damage prevention system for preventing damage to a tool used in a numerically controlled machine tool.
2. Description of the Related Art
In machine tools, a tool can be damaged due to abnormal load applied thereto during a cutting operation, and therefore, various measures are taken to prevent such damage. Tool damage prevention methods primarily rely upon the detection of cutting load, and typical methods for detecting the cutting load are as follows:
(1) A method using an external sensor arranged on a table, a tool holder or the like. PA1 (2) A method utilizing a current value of a spindle motor.
In the conventional method (1), however, a sensor must be arranged externally, and a control device for processing the sensor signal must be provided separately from a numerical control device, which leads to complicated arrangement and higher cost.
In the conventional method (2), since the current value of the spindle motor involves rotating load or acceleration/deceleration load of the spindle, the detection accuracy is poor and tool damage cannot be detected with accuracy.